Prominences on Other Stars

I am in the process of putting together a digital slideshow comprised
of h-alpha images of the Sun that I have taken and simulated images to
scale of other stars. The simulated images are being made from solar
images I have taken that are scaled up or down as appropriate and
"recolored" as appropriate.

In the course of putting this program together I got to thinking about
what a large prominence would probably look like on another star. I
have been unable to locate any information even speculating about
this. Primarily I am interested in hearing speculation as to how
large prominences could be on other stars. How do the laws of physics
apply? Given that a good prominence on our Sun can frequently extend
outward 50,000 miles and it is not that uncome to capture one
extending out to even 100,000 miles, can a good prominence on
Betelguese extend out proportionally as far (an amazing 50 million
miles or further) or would the limits for prominence size on other
stars be much like on our Sun? If so, a 50,000 mile to 100,000 mile
prominence extending above the limb of Betelquese, Antares or other
super red giant would barely be a bump on the surface.

What is the speculation of others, or better yet how would physical
laws and gravity apply?

Barry Simon

In message , Barry
Simon writes
I am in the process of putting together a digital slideshow comprised
of h-alpha images of the Sun that I have taken and simulated images to
scale of other stars. The simulated images are being made from solar
images I have taken that are scaled up or down as appropriate and
"recolored" as appropriate.

It is an interesting question.
Have any speckle images of Betelgeuse been made in H-alpha ?

this. Primarily I am interested in hearing speculation as to how
large prominences could be on other stars. How do the laws of physics
apply? Given that a good prominence on our Sun can frequently extend
outward 50,000 miles and it is not that uncome to capture one
extending out to even 100,000 miles, can a good prominence on
Betelguese extend out proportionally as far (an amazing 50 million
miles or further) or would the limits for prominence size on other
stars be much like on our Sun? If so, a 50,000 mile to 100,000 mile
prominence extending above the limb of Betelquese, Antares or other
super red giant would barely be a bump on the surface.

What is the speculation of others, or better yet how would physical
laws and gravity apply?

Surface gravity on a sphere of uniform density rho scales with its
radius. And for a main sequence star mass scales with radius cubed. Very
crudely:

g = GM/r^2

M = 4/3 pi rho r^3

so g = 4/3 pi rho G r

This is bad news for your would be prominence on a massive giant main
sequence star. It would get smaller as the stars mass increases like
1/M^(1/3).

However, red giants are vastly expanded and will not be as dense as the
sun so they can do some very interesting things. Planetary nebulae
result when stars lose their grip on the outer layers.

AGB or Mira class variable stars would be a good place to look for
interesting behaviour. Are any close enough or big enough to resolve?

Regards,
--
Martin Brown

In message , Barry
Simon writes
I am in the process of putting together a digital slideshow comprised
of h-alpha images of the Sun that I have taken and simulated images to
scale of other stars. The simulated images are being made from solar
images I have taken that are scaled up or down as appropriate and
"recolored" as appropriate.

It is an interesting question.
Have any speckle images of Betelgeuse been made in H-alpha ?

this. Primarily I am interested in hearing speculation as to how
large prominences could be on other stars. How do the laws of physics
apply? Given that a good prominence on our Sun can frequently extend
outward 50,000 miles and it is not that uncome to capture one
extending out to even 100,000 miles, can a good prominence on
Betelguese extend out proportionally as far (an amazing 50 million
miles or further) or would the limits for prominence size on other
stars be much like on our Sun? If so, a 50,000 mile to 100,000 mile
prominence extending above the limb of Betelquese, Antares or other
super red giant would barely be a bump on the surface.

What is the speculation of others, or better yet how would physical
laws and gravity apply?

Surface gravity on a sphere of uniform density rho scales with its
radius. And for a main sequence star mass scales with radius cubed. Very
crudely:

g = GM/r^2

M = 4/3 pi rho r^3

so g = 4/3 pi rho G r

This is bad news for your would be prominence on a massive giant main
sequence star. It would get smaller as the stars mass increases like
1/M^(1/3).

However, red giants are vastly expanded and will not be as dense as the
sun so they can do some very interesting things. Planetary nebulae
result when stars lose their grip on the outer layers.

AGB or Mira class variable stars would be a good place to look for
interesting behaviour. Are any close enough or big enough to resolve?

Regards,
--
Martin Brown